Long-cycle transistor astable multivibrator

ABSTRACT

A long cycle oscillator comprising a first and a second transistor, and a charge-discharge circuit including a capacitor and a resistor which are connected in parallel to each other, in which the said components are so constructed that a base current of the first transistor is controlled by a collector voltage of the second transistor, an applied voltage to the second transistor is controlled by the collector voltage of the first transistor, the base current of the second transistor being controlled by the collector voltage of the first transistor and the charge-discharge circuit.

United States Patent Oushige et al.

[54] LONG-CYCLE TRANSISTOR ASTABLE MULTIVIBRATOR [72] Inventors:Takayoshi Oushige; Kikuo Iizuka,

both of Hitachi, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22]Filed: March 10, 1970 [21] Appl. No.: 18,169

[30] Foreign Application Priority Data March 10, 1969 Japan ..44/l7517[52] US. Cl ..33l/l13 R, 318/227, 331/185 [51] Int. Cl. ..H03k 3/282[58] Field of Search....331/l l3 R, 144, 185; 318/227 [56] ReferencesCited UNITED STATES PATENTS 3,240,989 3/1966 Grunwaldt ..331/ll3X3,061,742 10/1962 Harrison ..33l/ll3X [4 1 Oct. 3, 1972 3,253,2345/1966- Kretzmer .331/113 FOREIGN PATENTS OR APPLICATIONS 1,030,8245/1966 GreatBritain ..331/113 Primary Examiner-Roy Lake AssistantExaminer-Siegfried H. Grimm AttorneyCra.ig, Antonelli and Hill [5 7]ABSTRACT A long cycle oscillator comprising a first and a secondtransistor, and a charge-discharge circuit including a capacitor and aresistor which are connected in.parallel to each other, in which thesaid components are so constructed that a base current of the firsttransistor is controlled by a collector voltage of the secondtransistor, an applied voltage to the second transistor is controlled bythe collector voltage of the first transistor, the base current of thesecond transistor being controlled by the collector voltage of the firsttransistor and the charge-discharge circuit.

7 Claims, 10 Drawing Figures PATENTEDncra m2 3.696.311

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5 IO I S RISING TIME (second) FIG. 9 A9 902 F9 E9 INVENTORS TAKAYO$HIMSHIG'E a d K KMO IIZHKA ATTORNEYj LONG-CYCLE TRANSISTOR ASTABLEMULTIVIBRATOR BACKGROUND OF THE INVENTION This invention relates to anoscillator utilizing the charging and discharging characteristics of acapacitor for control thereof.

There is as a typical oscillator, the astable multivibrator, whichutilizes the charging and discharging characteristics of a capacitor forcontrol. Because in accordance with the astable multivibrator verydesirable rectangular waves are produced easily by circuits which aresimple, they have been used widely in the field of digital controls.Recently, astable multivibrator have been used in many fields includingelectric fans, for example, because of their low-cost, easy manufactureand high reliability in operation.

A conventional astable multivibrator is provided with a pair oftransistors, and the collector of each of the transistors isrespectively connected through a resistor to the power supply. Since thecollector currents of the respective transistors are controlled only bytheir base currents and the operating point of each of the transistorslies on a straight load line which can be determined by values of thesupply voltage and the resistors connected between the power supply andthe respective collectors, only the initial part of the chargedischargecharacteristics of the capacitors contributes to oscillation. Therefore,the cycle of the conventional astable multivibrator necessarily isshorter than the time constant which is determined by the capacitor andthe resistor in the charge-discharge circuits. Because the conventionalastable multivibrator has a pair of charge-discharge circuits and thecharge and discharge of respective charge-discharge circuits are causedby mutual interferences, the. transistors necessarily are turned on oroff, alternatively. Therefore, from its turn off-tum on characteristics,the output voltage cannot be controlled. If the resistance of theresistor for discharging is made too large, the base currentconsiderably decreases, so that the transistor cannot switch on to stopthe oscillation of the oscillator. Though, in order to lengthen thecycle of the oscillation, it may be thought to increase the capacity ofthe capacitor, a sufficiently large capacitance within its limited sizecannot be obtained from the practical view point of manufacturing thecapacitors.

Since a pair of charge-discharge circuits are employed in theconventional astable multivibrator, the relationship between therespective charge-discharge circuits is disturbed by fluctuation of thesupply voltage to stop the oscillation. In addition, when the supplyvoltage is applied to the oscillator circuit, it is impossible todetermine which transistor will switch on first between the pair oftransistors. In a long cycle oscillator, to know which transistor willswitch on first is very important in order to operate the devices orapparatus employing the oscillator without wasting operation time.

SUMMARY OF THE INVENTION capable of changing the oscillating cycle oververy wide ranges.

It is another object of the present invention to provide an oscillatorof the type described in which very long cycles can be generated, inspite of its use of a small capacity capacitor.

It is a further an object of the present invention to provide anoscillator which can continue to provide good oscillation, even if thesupply voltage is not stable.

It is still another object of the present invention to provide suchoscillator which is capable of continuously changing the output wavefonns.

It is still a further object of the present invention to provide anoscillator having a simple circuit.

An oscillator in accordance with the invention has first and secondtransistors. Since the collector of the first transistor is connected tothe supply through a resistor, if the supply voltage is constant, theload line on which an operating point of the first transistor lies isalmost linear. On the other hand, since the collector of the secondtransistor is connected to the collector of the first transistor, itsload line on which the operating point of the second transistor lies canbe controlled by the collector voltage of the first transistor. Bychanging the base current of the second transistor, the operating pointof the second transistor can be optionally selected over the whole loadline controllable by the collector voltage of the first transistor. Inaddition, as the base of the first transistor is connected to thecollector of the second transistor, the collector voltage of the firsttransistor returns to the base of the first transistor. As a result, theoperation of the first and second transistors can be controlled only bythe charge-discharge circuit; and, even if the supply voltage frequentlychanges, the oscillator of the invention continues to provide goodoscillation. In addition, good oscillation is continued only by thetum-off of the second transistor, without turning off and turning on thefirst transistor and the first and second transistors. Therefore, overthe very wide range of the resistance of the resistor a variation in thedischarging time can be expected to change the oscillation cycles over avery wide range, in accordance with the present invention. As theoscillation can be continued without turning on the first transistor,the output wave form is also changed continuously. In the case where thecharge voltage of the charge-discharge circuit is nearly equal to zero,the collector current of the first transistor can be decreased instantlyand the collector current of the second transistor is increased. Theabove-mentioned characteristics can also be observed in the case wherethe supply voltage is applied to the oscillator circuit.

BRIEF DESCRIPTION OF THE DRAWING The present invention is hereinafterparticularly described with reference to the accompanying drawing, inwhich:

FIG. 1 is a principle circuit embodying the present invention;

FIG. 2 shows wave forms relative to voltage and current obtained by thecircuit shown in FIG. 1;

FIG. 3 is a circuit diagram of a modified form of the circuit of FIG. 1;

FIG. 4 is a graph showing a relationship between oscillating cyclesdiagram and the resistance of the resistor in charge-discharge circuitin FIG. 3;

FIG. 5 is a circuit diagram whose oscillator circuit in FIG. 3 is usedfor controlling a motor of an electric fan;

FIG. 6 shows a variation in speeds of outdoor wind;

FIG. 7 shows a wave form of the variation in wind speeds produced by themotor circuit of the electric fan shown in FIG.

FIG. 8 is a graph showing the starting characteristics of the motor ofelectric fan shown in FIG. 5; and

FIG. 9 and FIG. 10 are diagrams of circuits to be used as a rectifiercircuit in the oscillator circuit shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, there isshown a principle circuit for explaining an oscillator of the invention;in which the collector, emitter and base electrodes of a transistor 1are respectively connected to a positive terminal A of a supply 5through a resistor 3 and a switch 4, to a negative terminal B and to thecollector of a transistor 2. The collector, emitter and base electrodesof the transistor 2 are respectively connected to the collector oftransistor 1 through a variable resistor 6, to the negative terminal Band to the collector of transistor 1 through a'charge-discharge circuit7 which comprises a capacitor 8 and a variable resistor 9. Though inFIG. 1 n-P-n transistors are used as the transistors 1 and 2, it goeswithout saying that the transistors can be replaced by P-n-P transistorswith suitable change in the polarity of the bias.

FIG. 2 shows the waveforms generated by the unstable multivibrator shownin FIG. 1, in which the waveform A represents the collector voltage offirst transistor 1, waveform B represents the charge voltage ofcapacitor 8, and waveform C shows the base current of transistor 2. Whenthe switch 4 is turned on, the supply voltage is applied to thecollectors of transistor 1 and transistor 2. The collector current i oftransistor 1 begins to flow due to the base current i of the transistor1 flowing from the supply 5 through the resistor 3 and variable resistor6, and consequently, the collector voltage of the transistor 1decreases. The collector current i of the transistor 2 will begin toflow also due to the base current i, of the transistor 2 flowing fromthe supply 5 through the resistor 3 and the chargedischarge circuit 7,and consequently, the collector voltage of the transistor 2 decreases.

The relationship between the collector current i of the transistor 2 andbase current i of the transistor 1 is usually given by i5 i3 i2 wherethe current i is a current flowing through the variable resistor 6. Withthe decreasing of the collector voltage of the transistor 1 and the basecurrent i., of the transistor 2 as capacitor 8 charges, the collectorcurrent i of the transistor 2 decreases. Since the current i isdecreased by decreasing the collector voltage of the transistor 1, thebase current i necessarily decreases, but this causes the collectorvoltage of the transistor 1 to increase. The rate of increase in thecollector current i entering the transistor 2 is larger than that of thecurrent i As a result, the collector current i of the transistor 2becomes very large, but the collector current i of the transistor 1becomes very small. When the value of the base current i, entering thetransistor 2 is large enough to saturate the collector current ientering the transistor 2, the transistor 2 is turned on and thetransistor 1 is turned off.

Due to the base current i., flowing through the' capacitor 8, thecapacitor 8 is charged and the base current i, begins to decreaseexponentially. The base current i., is decreased by the charging of thecapacitor 8, and the collector current 1}, of the transistor 2decreases, while the base current i of the transistor 1 increases. Withincreasing current i the collector voltage of transistor 1 decreases tocause a suppressing of the increase of current i with slow decrease inthe collector voltage of transistor 1.

Up to the time of complete charging of capacitor 8, the base potentialof the transistor 2 is lower than the collector voltage of transistor 1.The charging voltage of the capacitor 8 corresponds to the differencebetween the collector voltage of transistor 1 and base voltage oftransistor 2. When the potential at the base J of the transistor 2becomes negative, the base current i,

and collector current i of the transistor 2 are equal to zero. Thecurrent i through the variable resistor 6 is equal to the base current iof the transistor 1 and its collector voltage becomes low level.

In FIG. 2, T and T, respectively show the times of switching on andturning off, wherein the collector voltage A of transistor 1 reaches themaximum value. If the base current i., flowing into the transistor 2, asdenoted by the line C in FIG. 2, is a large enough value to saturate thecollector current of the transistor 2, the collector voltage oftransistor 2 will be constant until the base current i flowing into thetransistor 2 reaches a valve smaller than the value sufficient tosaturate the collector current, as denoted by the line D in FIG. 2. Thecharge voltage of the capacitor 8 increases toward the level of thecollector voltage of the transistor 1, so that the base current flowinginto the transistor 2 decreases towards zero. If no collector current iof transistor 2 flows at the point T the collector voltage of transistor1 becomes low level, as denoted by the line A in FIG. 2.

The base current i entering the transistor 1 is changed by adjustment ofvariable resistor 6 and therefore, the level of the collector voltage ofthe transistor 1 can be controlled by adjusting the resistance ofvariable resistor 6.

When the emitter-to-base voltage of the transistor 2 is negative, thecapacitor 8 beingsto discharge through the variable resistor 9. As thecharge of the capacitor 8 decreases, the potential at the base oftransistor 2 increases toward the collector voltage of the transistor 1.On the other hand, when at the time T2 the emitter-tobase voltage of thetransistor 2 is positive, both the base current i entering transistor 2and the collector current i of the transistor 2 begin to flow, and thebase current i flowing into the transistor 1 decreases. Decrease in thebase current i flowing into the transistor 1 causes an increase in thecollector voltage of the transistor 1. The base current i., flowing intothe transistor 2 through the capacitor 8 considerably increasesconcurrently with the increase of collector current i;, entering thetransistor 2 and the considerable decrease of base current i enteringthe transistor 1. When the collector current i flowing into thetransistor 2 has a very small value, the base current i flowing into thetransistor 2 charges the capacitor 8 again. In this way the oscillationof the oscillator can be continued.

Referring to the FIG. 2, the length of time between the T1 and T2 iscontrolled by changing the value of the variable resistor 9. The valueof the collector voltage of transistor 1 is constant until the basecurrent flowing into the transistor 2 begins to flow again, i.e., in theregion between T1 and T2. At time T2, when the charge voltage of thecapacitor 8 represented by curve B is nearly equal to zero and theemitter-to-base voltage becomes positive, the base current i., flowinginto the transistor 2 instantaneously increases (line C) concurrentlywith increase of the collector voltage of the transistor 1. At the sametime, the collector voltage of the transistor 1 considerably changesagain over a very wide range.

FIG. 3 shows an oscillating circuit of the invention, in which thecollector electrode of a transistor 304 is connected to a positiveterminal A3 of a supply 301 through a load resistor 303 and switch 302,the base electrode of the transistor 304 is connected to the collectorof a transistor 305, the emitter of the transistor 304 is connected to anegative terminal B of the supply 301 through a resistor 306, and thecollector of the transistor 305 is connected to the collector of thetransistor 304 through the resistor 307 and variable resistor 308. Thebase of the transistor 305 is connected through a charge-dischargecircuit 309, resistor 310, and diode 311 to a point C3 which isconnected to the variable resistor 308 and the resistor 307. A capacitor312 which is connected between the collector and the base of thetransistor 305, and the resistor 313 is connected between the base ofthe transistor 304 and the negative terminal B of the supply 301. Saidchargedischarge circuit 309 employs a capacitor 315 and a variableresistor 314. The capacitor 315 is connected at the points D and E inparallel with the variable resistor 314.

As stated above, when the switch 302 turns on, the supply voltage isapplied to the collectors of the transistors 304 and 305, so that thebase current of the transistor 30S begins to flow through the resistor303, the variable resistor 308, diode 311, resistor 310, and thecharge-discharge circuit 309 from the supply. As a result, the collectorvoltage of the transistor 304 reaches the maximum value, the collectorvoltage of the transistor 305 reaches a minimum value, and the basecurrent entering the transistor 305 begins to charge the capacitor 315.The charging of the capacitor 315 will continue until the base potentialat the transistor 305 becomes negative.

When the base potential of transistor 305 becomes negative, thetransistor 305 is switched to the off stage and the collector voltage atthe transistor 304 reaches minimum value. As the current flowing throughthe variable resistor 308 is almost equal to the base current enteringthe transistor 304, the minimum value of voltage at the collector of thetransistor 304 may be regulated by changing the value of the variableresistor. When the base current flowing into the transistor 305 cannotflow through the charge-discharge circuit 309 because the capacitor 315is fully charged, the electric charge of the capacitor 315 begins todischarge through the variable resistor 314. The discharging period ofthe capacitor 315 is therefore controlled by variation of the value ofthe variable resistor 314; the larger the value of the variable resistor314 is made, the longer will be the discharging period produced. In casethe charge voltage of the capacitor 315 becomes very small, the basepotential at the transistor 305 becomes positive, and the collectorvoltage at the transistor 304 can be suddenly shifted to the high level,and consequently, the base current flowing into the transistor 305begins to flow through the charge-discharge circuit again. The diode 311prevents the transistor 305 from breakdown due to theinverse-directional application of the charge voltage of capacitor 315.The resistor 310 permits only flow of a small amount of the base currententering the base of transistor 305, and determines the value of thecharging current of the capacitor 315. If the resistor 310 is large,charging current for the capacitor 315 will be small. Furthermore, sincethe capacitor 315 is charged very slowly, the flow of the collectorcurrent of the transistor 305 is prolonged thereby to lengthen theoperating time of the transistor 305. If the resistor 310 is small, thecharging of the capacitor 315 will be performed rapidly and theoperating time of the transistor 305 becomes short. Since the value ofthe base current flowing into the transistor 305 is determined by theresistor 310, irrespective of any variation of the variable resistor314, the value of the variable resistor 314 is changable over a widerange from large values to small values, and the repetition number ofthe pulses per unit time can be continuously changed over a wide range.Since the capacitor 312 is connected between the base and the collectorof the transistor 305, even if the supply voltage changes frequently inthe manner of a pulsating voltage, the oscillator of the invention willcontinue to oscillate and the capacitor 312 will rapidly absorb thenoise produced by the changing collector voltages of the transistors 1and 2.

FIG. 4 shows the variation of the oscillation cycle produced by thevariable resistor 314, in which the horizontal axis shows resistances ofvariable resistor 314 and the vertical axis shows cycles of pulsation.In the example, the supply voltage was a pulsating voltage with V and afrequency of Hz produced by rectifying the alternating voltage, the loadresistor 303 was 1.0 k 0 the resistor 306 was 22 Q, the resistor 307 is4.0 k (I, the resistor 313 was 10 k 0, the resistor 310 was 300 k 0, andthe capacitor 315 was 10 p. F. The value of the variable resistor 308was selected to be zero 0, and transistor 304 and transistor 305respectively had low frequency amplifications of about 100 and had alarge backward resistance. These transistors were made of silicon, andthe diode 311 had a large value of backward resistance. Though FIG. 4shows only the range where the value of the variable resistor is from 10M Q to about 0.7 M Q, if the value of the variable resistor 314 islarger than 10 M Q, the cycle of the oscillation becomes longer still,and if the value of the variable resistor 314 is smaller than 700 k 0,the cycle of the oscillator becomes shorter still.

As one embodiment of the invention, a circuit using a motor substitutedfor the resistor 303 shown in FIG. 3 is illustrated in FIG. 5. A mainwinding 501 is connected to the line through a switch 505 at a pair ofinput terminals A5 and B5, and an auxiliary winding 502 and a capacitor503 which are connected in series with each other and are respectivelyconnected in parallel with the main winding 501. A motor circuitcomprises the main winding 501, the auxiliary winding 502 and thecapacitor 503. Input terminals C5 and D5 of a full-wave rectifier 501comprising four diodes are connected in parallel with the auxiliarywinding 502 of the motor, and output terminals G and H5 of the fullwaverectifier 507 are connected to an oscillator circuit 511 through a surgeabsorber 525 comprising a diode 508, a capacitor 509, and a varistor510. The oscillator 511 corresponds to the circuit shown in FIG. 3except for the switch 512.

In the oscillator circuit 511, a transistor 515 is connected between twooutput terminals G5 and H5 of the full-wave rectifier 507, so that thecollector is connected to the positive terminal GS of the rectifier 507and the emitter is connecter to the negative terminal H5 of therectifier. A resistor 516 is connected between the emitter of thetransistor 525 and the negative terminal H5 of the rectifier. One end ofa variable resistor 517 is connected to the collector of the transistor515 and the other end is connected to a resistor 519 and a diode 522.One end of the resistor 519 is connected to the variable resistor 517and the other end is connected to the collector of the transistor 518.The diode 522 is connected from the variable resistor 517 and theresistor 519 to the resistor 521. One end of the resistor 521 isconnected to the diode 522 and the other end is connected to thecharge-discharge circuit 523 employing a capacitor 526, a variableresistor 527 and the switch 512. The variable resistor 527 is connectedin parallel with the capacitor through the switch 512. A capacitor 524is connected between the collector and the base of the transistor 518,of which the collector is connected to the base of the transistor 515and the emitter is connected to the negative terminal H, of therectifier and the resistor 516, respectively. Both the motor circuit 504and the full-wave rectifier correspond to the load resistor 303 shown inFIG. 3.

FIG. 6 shows wind speed variation of natural outdoor wind v.s. time.From this FIG. 6, it will be found that there is a constant cycle in thecomplicated variation of the wind speed. It is said that the naturaloutdoor wind makes people feel more comfortable than artificial windsince there are delicate changes of the wind speeds in the natural wind.According 'to the circuit shown in FIG. 5, in which an electric fanmotor is used for the motor circuit, the rotation speed of the electricfan motor can be controlled by using the oscillator of the invention,and by the electric fan using the oscillator of the invention the samewind as the natural outdoor wind can be produced. It is essential forproducing such a variable wind that the rotation speed of the electricfan motor can be changed with a considerably long .cycle.

Referring to FIG. 5, the motor is provided with the auxiliary winding502 and the main winding displaced 90 electrical degrees from eachother. The main winding 501 is connected directly to the alternatingsupply through the switch 505, and the auxiliary winding 502 having acapacitor 503 connected in series therewith is connected in parallelwith the main winding. The phase of current in the main winding 501 lagsfrom that of the supply voltage, while the current in the auxiliarywinding 502 precedes that of the supply voltage. As a result, thecurrents in the two windings are displaced nearly 90 in phase from eachother and therefore, a uniform rotating magnetic field can be produced.The torque of the motor will be developed by the electromagnetic actioncaused between the current in the rotor and the uniform rotatingmagnetic field. Accordingly, it is possible to control the motor speedof the electric fan by changing the value of the current into the mainwinding or auxiliaryv winding, or of the phase difference between thecurrents in the stator windings.

The circuit shown in FIG. 5 provides the way to control the torque ofthe motor by changing the current in the auxiliary winding. When boththe switch 512, employed in the charge-discharge circuit, and the switch505 are switched on, the alternating current flows into the two statorwindings and the capacitor from the supply through the switch 505, andthe terminal voltage of the auxiliary winging is applied to theoscillator circuit through the full-wave rectifier 507 and the surgeabsorber 525. As already explained, in conjunction with FIG. 3, if thevoltage is applied to the oscillator circuit 511, the collector voltageat the transistor 518 becomes low, and the collector voltage at thetransistor 515 becomes high. Thus, the current entering the oscillatorcircuit 511 becomes minimum and the current into the auxiliary windingbecomes maximum. As a result, when the rotor of the motor begins torotate, the starting torque also becomes maximum.

With charging of the capacitor 526 employed in the charge-dischargecircuit, the current flowing into the oscillator circuit 511 through thefull wave rectifier becomes large and finally, the current flowing intothe oscillator circuit 511 becomes maximum. As a result, the rotatingspeed of the motor becomes minimum. During discharging of the capacitor526 employed in the charge-discharged circuit 523, the rotating speed ofthe motor is minimum. In this case, as the transistor 518 is cut off,the current flowing through the variable resistor 517 is nearly equal tothe base current flowing into the transistor 515. The base current ofthe transistor 515 will be controlled by changing the value of thevariable resistor 517. As a result, since the current entering theoscillator circuit will be controlled by changing the value of thevariable resistor 517, the minimum level of the rotating speed of themotor is controlled by changing the variable resistor 517. The variationof the wind produced by the electric fan shown in FIG. 5 is illustratedin FIG. 7.

In this embodiment, components employed in FIG. 5 were as follows, thetransistor 515 was 2SC454C, transistor 518 was 2SC685A, the value of thevariable resistor 517 was zero, the value of the resistor 516 was 22 Q,the value of the resistor 519 was 4 k 0, the value of the resistor 520was 12 k (I the diode 522 was 185313, the value of the capacitor 509 was3.3 p. F, the varistor 510 was S-TDlOO, and the diodes 506 beingemployed in the full-wave rectifier were BS-4. The voltage supply has avalue in the order of volts with 50 Hz frequency. In spite ofapplication of the pulsating voltage produced by rectifying thealternating voltage which tends to deteriorate the oscillation, as theoscillator of the invention is not controlled by plural chargedischargecircuits but only by one charge-discharge circuit, good oscillation canbe expected. Furthermore, because the capacitor is connected between thebase and collector of the transistor 518, the above characteristic isimproved, if the oscillating cycle is much longer than the time duringwhich the current flowing in the oscillator is nearly equal to zero.

In case the switch 512 is opened, the switch 505 is also opened. Thepulsating current being produced by rectifying the alternating currententers the oscillator circuit 511, and at the same time the base currentof the transistor 518 flowing into the capacitor 526 lowers thecollector voltage of the transistor 518 and the collector currentflowing into the transistor 515. Contrary to the decrease in the currententering the oscillator, the values of the current flowing into theauxiliary winding and the starting torque become large. When thecharging voltage between the terminals of the capacitor 526 is of largevalue, the base current flowing into the transistor 518 will be almostequal to zero. Therefore, the transistor 518 is cut off and the rotatingspeed of the motor is reduced to a minimum. As already explained, thecurrent flowing into the resistor 519 will be nearly equal to the basecurrent flowing into the transistor 515 and the minimum level of therotating speed of the motor can be controlled by changing the variableresistor 517. If the leakage current of the capacitor 526 and thebackward current through the transistor 515, the transistor 518 anddiode 522 are almost zero, theoscillation does not take place.Therefore, in this case the wind strength produced by the electric fanis not changable. If the rotationspeed of the motor isset at 400 rpm byadjusting the variable resistor 517, the characteristics of the startingspeed can be shown in FIG. 8, in which example the supply voltage was100V with a frequency of 50 Hz as defined by curve A, and in anotherexample the supply voltage was 100V with a frequency of 60 Hz as definedby curve B. In FIG. 5, if full-wave rectifier 507 is connected inparallel with the capacitor 503, it can be expected that an effectsimilar to the above will be obtained. In the case when the currentflowing into the oscillator 511 through the full-wave rectifier is ofsmall value, the currents in the two windings are respectively displacednearly 90 in phase and the rotating speed of the motor is increased.

On the other hand, with increasing of the current flowing into theoscillator 511, the phase difference between the two currents in the twowindings becomes small, then the rotating speed is decreased. Instead ofthe full-wave rectifier, a half-wave rectifier can be employed in theoscillator of the invention. An oscillator using the circuit shown inFIG. 9, which is substituted for the surge absorber and the full waverectifier, will also cause good results. The terminals A9 and B9 areconnected to the oscillator 511 and the tenninals C9 and D9 areconnected to the motor, respectively. A resistor 902 is connectedbetween the terminal A9 and the anode F9 of a silicon controlledrectifier 905 of which the anode and cathode are respectively connectedto output terminals E9 and F9 of a full-wave rectifier. A resistor 903is connected between the terminals A9 and B9, and a capacitor 904 isconnected between the terminal B9 and the cathode G9 of thesilicon-controlled rectifier 905. A bi-directional diode thyristor 906is connected between the terminal B9 and a gate terminal E7 of thesilicon-controlled rectifier 905. As stated already, the pulsatingcurrent is produced by rectifying the alternating current which flowsinto the oscillator circuit from the motor through the terminals A9 andB9, to bring about the oscillation, and the amount of the currentflowing into the oscillator is changed with the oscillation cycle. Theresistance between the terminals A9 and B9 is changed with the cycle ofthe oscillation. The voltage at the terminal B9 rises with theincreasing of the supply voltage, and the conduction of the siliconcontrolled rectifier starts at the angle, where the applied voltage atthe terminal B9 becomes equal to the critical switching voltage of thebi-directional diode thyristor 905. When the resistance between theterminals A9, B9 becomes large, the angle where the conduction of thesilicon controlled rectifier starts becomes large and the conductionangle of the silicon controlled rectifier becomes small. As a result,the rotating speed of the motor increases. On the other hand, as theresistance between terminals A9, B9 is decreased, it is possible tolengthen the time during turning-on of the silicon controlled rectifierin one cycle of the pulsating voltage produced by rectifying thealternating voltage. As a result, the torque of the motor becomes low invalue to decrease the rotating speed of the motor.

In FIG. 5, the circuit shown in FIG. 10 which is substi tuted for thefull-wave rectifier 507, can also cause good results. Input terminalsA10 and'BlO are connected to the motor, both anode and cathode of a bidirectional triode thyristor are respectively connected to terminals A10and B10. A resistor 1001 is connected between two terminals A10 and C10,and a resistor 1002 is connected between a pair of input terminals C10,D10 of the full-wave rectifier. A capacitor 1003 is connected betweenthe terminal D10 and a cathode terminal B10 of the bi-directional triodethyristor, and a bi-directional diode thyristor 1004 is connectedbetween the terminal D10 and a gate terminal E10 of the bi-directionaltriode thyristor. Output terminals F10 and G10 of the full-waverectifier are respectively connected to the terminals of the oscillatorcircuit.

In FIGS. 9 and 10, the conduction angle of the thyristor 1005 and thesilicon controlled rectifier 905 are controlled by the oscillation. Whenthe conduction angle is large, the rotating speed decreases. When theconduction angle is small, however, the rotating speed increases.

Though the transistors are used in the oscillators shown in FIGS. 1, 3and 5, the transistors can be replaced with other switching components,provided that they have an amplification function, and their maincurrent can be controlled by controlling current in which the maincurrent and controlling current respectively correspond to the collectorcurrent and the base current of the transistors in the above examples.For example, vacuum tubes, field effect transistors and siliconcontrolled rectifiers may be used as well as the transistors. It will beunderstood that examples shown in FIGS. 9 and 10 can be employed for theoscillator to be utilized with considerably large loads.

Although the present invention has been described with reference to buta single embodiment, it is to be understood that the scope of theinvention is not limited to the specific details thereof, but issusceptible of numerous changes and modifications as would be apparent.to one with normal skill in the pertinent technology.

What we claim is:

1. An oscillator comprising a first and a second switching component,respectively, each having an amplification function, first and secondmain current electrodes, and being capable of controlling its maincurrent in response to an applied controlling current at a control inputthereof, -a load and a supply voltage source connected in .seriesbetween said first and 7 second electrodes of said firstswitchingcomponent,

and a charge-discharge circuit connected between said first electrode ofsaid first switching component and the control input of said secondswitching component and having a predetermined time constant throughwhich said controlling current of said second switching component ischanged by said main current of said first switching component, wherebya voltage to be applied to said second switching component is controlledby said main current of said first switching component, and meansconnecting the first electrode of said second switching component to thejunction of said load and said first electrode of said first switchingcomponent, said control input of said first switching component beingconnected to said first electrode of said second switching componentwhereby said controllingcurrent of said first switching component iscontrolled directly by said main currents of said first and secondswitching components and the second electrodes of said first and secondswitching components being directly connected together.

2. An oscillator according to claim 1, in which said first and secondswitching components are a first and a second transistor, respectively,whereby the collector current of said second transistor is controlled bythe collector voltage of the first transistor, the base of the secondtransistor being connected through said chargedischarge circuit to thecollector of the first transistor, the collector of said secondtransistor being connected through a variable resistance to thecollector of said first transistor, the emitters of said first andsecond transistors being connected together and the base of the firsttransistor being connected to the collector of the second transistor.

3. An oscillator comprising a first transistor having a collector and anemitter; a voltage supply; a first resistor connected between thecollector of the first transistor and one side of said voltage supply; asecond transistor having a collector connected to the base of the firsttransistor and an emitter connected to the emitter of the firsttransistor; a second resistor connected between the collectors of thefirst and second transistors; a first capacitor connected between thecollector of the first transistor and the base of the second transistor;and a third resistor connected in parallel to said first capacitor.

rectifier circuit and said load, and a base; a second transistor havinga collector connected to the collector of said first transistor througha first resistor, an emitter connected to said alternating currentsupply through said rectifier and said load and a base connected to thecollector of said first transistor through a chargedischarge circuit;the base of said first transistor being connected to the collector ofsaid second transistor.

6. An oscillator according to claim 5, including a first capacitorconnected between the collector and base of said second transistor, asecond resistor connected between the base and emitter of said firsttransistor and a third resistor connected between the emitter of saidfirst transistor and said rectifier circuit.

7. An oscillator as defined in claim 5, wherein said rectifier circuitis connected to a circuit comprising a silicon controlled rectifier ofwhich an anode and a cathode are respectively connected to outputterminals of said rectifier circuit, a second resistor connected betweensaid anode of said silicon controlled rectifier and a third resistor, afirst capacitor connected between said third resistor and said cathodeof said silicon controlled rectifier, a bi-directional diode thyristorconnected between a gate of said silicon controlled rectifier and bothsaid first capacitor and said third resistor, and the third resistorconnected between two input terminals of said oscillator.

1. An oscillator comprising a first and a second switching component,respectively, each having an amplification function, first and secondmain current electrodes, and being capable of controlling its maincurrent in response to an applied controlling current at a control inputthereof, a load and a supply voltage source connected in series betweensaid first and second electrodes of said first switching component, anda charge-discharge circuit connected between said first electrode ofsaid first switching component and the control input of said secondswitching component and having a predetermined time constant throughwhich said controlling current of said second switching component ischanged by said main current of said first switching component, wherebya voltage to be applied to said second switching component is controlledby said main current of said first switching component, and meansconnecting the first electrode of said second switching component to thejunction of said load and said first electrode of said first switchingcomponent, said control input of said first switching component beingconnected to said first electrode of said second switching componentwhereby said controlling current of said first switching component iscontrolled directly by said main currents of said first and secondswitching components and the second electrodes of said first and secondswitching components being directly connected together.
 2. An oscillatoraccording to claim 1, in which said first and second switchingcomponents are a first and a second transistor, respectively, wherebythe collector current of said second transistor is controlled by thecollector voltage of the first transistor, the base of the secondtransistor being connected through said charge-discharge circuit to thecollector of the first transistor, the collector of said secondtransistor being connected through a variable resistance to thecollector of said first transistor, the emitters of said first andsecond transistors being connected together and the base of the firsttransistor being connected to the collector of the second transistor. 3.An oscillator comprising a first transistor having a collector and anemitter; a voltage supply; a first resistor connected between thecollector of the first transistor and one side of said voltage supply; asecond transistor having a collector connected to the base of the firsttransistor and an emitter connected to the emitter of the firsttransistor; a second resistor connected between the collectors of thefirst and second transistors; a first capacitor connected between thecollector of the first transistor and the base of the second transistor;and a third resistor connected in parallel to said first capacitor. 4.An oscillator according to claim 3, including a second capacitor whichis connected between the base and the collector of said secondtransistor, a fourth resistor connected between the other side of saidvoltage supply and the base of said first transistor and a fifthresistor connected between the emitter of the first transistor and theother side of said voltage supply.
 5. An oscillator comprising a firsttransistor having a collector connected through a rectifier circuit anda load to an alternating current supply, an emitter connected to thealternating current supply through said rectifier circuit and said load,and a base; a second transistor having a collector connected to thecollector of said first transistor through a first resistor, an emitterconnected to said alternating current supply through said rectifier andsaid load and a base connected to the collector of said first transistorthrough a charge-discharge circuit; the base of said first transistorbeing connected to the collector of said second transistor.
 6. Anoscillator according to claim 5, including a first capacitor connectedBetween the collector and base of said second transistor, a secondresistor connected between the base and emitter of said first transistorand a third resistor connected between the emitter of said firsttransistor and said rectifier circuit.
 7. An oscillator as defined inclaim 5, wherein said rectifier circuit is connected to a circuitcomprising a silicon controlled rectifier of which an anode and acathode are respectively connected to output terminals of said rectifiercircuit, a second resistor connected between said anode of said siliconcontrolled rectifier and a third resistor, a first capacitor connectedbetween said third resistor and said cathode of said silicon controlledrectifier, a bi-directional diode thyristor connected between a gate ofsaid silicon controlled rectifier and both said first capacitor and saidthird resistor, and the third resistor connected between two inputterminals of said oscillator.